Hello
since longer time I do work happy with LMDE2 and would like to know more about how to get into debugging and Support.

My preference is the Mate Desktop.

Github is not new for me, i just have a bit a trouble to see the overview of the whole LMDE distro config things.

Example, where can i find LMDE Mate info's about the Grub configuration and where would i have to make a request when i would like to propose a change?
Or Where would i check LMDE Mate specific configs?
How do i see the actual configuration stuff of an GTK specific application for LMDE?

I don't think the GRUB configuration is on GitHub. You can try talking to the Linux Mint developers on IRC in their channel #linuxmint-dev. See tips for how to best make use of #linuxmint-dev on http://developer.linuxmint.com/contributing.html. To join, just open HexChat from your menu and that will connect you to the Linux Mint IRC channels. Type /join #linuxmint-dev there to open the #linuxmint-dev channel as well.

For any file that you want to find from which package it came (so you can figure out what GitHub repository to look in), you can run the command dpkg -S /path/to/file to have your package manager check if it knows from which package that file was installed.

Several developers work on both the MATE Desktop and on Linux Mint. The MATE Desktop teams has its own GitHub here https://github.com/mate-desktop/. Several MATE Desktop programs, like Pluma (their text editor) and eom (their image viewer) and atril (their document viewer), aren't installed by default on LMDE 2 as LMDE 2 uses the Xapps. The MATE Desktop developers have their own IRC channels, see https://wiki.mate-desktop.org/irc.

ciaobello wrote:How do i see the actual configuration stuff of an GTK specific application for LMDE?

What kind of configuration do you want to see? The build configuration? That is found in the GitHub project.

Looking in GitHub gets you the development version. If you want to see the exact files as used to build the software as installed currently on your system, you can download the source package for that. First open Software Sources from your menu, and make sure "Enable source code repositories" is marked. Then click "Update the cache". This allows for downloading source for packages. Then you can use the command apt source [i]package-name[/i] to download the sources from which package-name was built.

Just i would like it more specified for LMDE development. I will create a repository on github to share the knowledge afterwards.
Please just mention if you have something to contribute to LMDE2 or LMDE3 to keep things apart.